Tension control for hacksaw blades



Jan. 30, 1951 w. H. SHORTELL 2,539,796

TENSION CONTROL FOR HACK SAW BLADES Filed Oct. 18, 1945 c" 6 C Q? I I I 3 F WW4 a A a M a W ,L

INVENTOR l i mu/w M J/mEnEZL Patented Jan. 30, 1951 F IiC'E TENSION CGNTROLFOR HACKSAW BLADES.

WilliamiHI shorten? Greenfield; Mass, assignor tWMilleis Fans Company, Greenfield; Massi, a corporation of Massachusetts:

Application October 18, 1945,"SerialNo; 6 22357 ,Tl'iis" invention relates to tension control for" hack'saw blades and constitutes an improvement over the'tensionfgauge for hack saw blades-shown in ,my. patent, No, 2,337,629;

The object of th'e invention is to provide meansfor controlling the reactive effect of the tension springhiri a device such asthat' shown in my patent above referred to; or in: any other construction'in. which resilient"tei1lsi'on' is imposed upon a hack saw blade when in'use; andthereby eliminate. possibility of injury to the'various parts of thecombined mechanism,orebystanders, should breakageioccur, as by strippingof a stud or the stripping of threads, such that the control'of the spring pressure is. relieved and violent reaction ofithe spring permitted.

Other objects of the. invention will. in part "be obvious and will in part appear-hereinafter,

The inventionaccordingly "comprises-the features'of construction; combination of elements, andarrangement ofiparts; which will be exemplifiedyiin theconstructions hereinafter .set forth,

and the scopewof therapplicatien of which will be i indicatedzin the claims;

For a ful-ler understanding of the natureand objects of the invention reierenceshould be had.- to the" following: detailed description; taken A inconnection w-1th the accompanying: drawing, in which 1 Fig. l-is a'side elevational-viewof afpowerzhack saw; ShWing.-;l3he general relation- ,of parts;

Fig. 2 is a view of one end of the tensionindevice-and: gauge as it appears in top plan;

Fig. 3 is a section showing the tension device and gauge with"myirnprovementfor preventing violent reaction of the 'tensioning springin case of'any breakage which would otherwise. result in release and violent reaction of "thespringj and Fig. 4 is-a cross sectional view on the line 4-5 of Fig: 3."

Asishown' in Fig. l the general organifiationi of apower'ha'ck sawmachine-includes a savr fraine A'whi-ch carries -the-sawblade B in a customary way between'thetwo-armsn, a? This sa'w' fi 'ame 7 may be recipro'catedf'irruany nonventional manner as byithe connectingrod.C,,.pivoted at one endotocthe'sawef'rameiA and' atits-other end-c to a rotatinggmember D1 carried-upon the shaftaE and drivenffrom any desired source ot power.

Saw frame A carries upon a projecting stud F a weight G which when adjusted along the stud F adjusts the downward weight upon blade B. The saw frame carries at its other end a stud shaft H passing freely through a sleeve Kcarried by 2. a' -suppo'rt liupon'the frame M. The "worker work Carnegie indi'oated'at O.

Saw'blade B'is' pierced at its ends with hol'es through wh'ich pass" studs 123 b at each endiori mounting it in the ordinary-aridconventional way between afiXed stud a carried'byleft-hand arm a. and stud- Which-pasSesfreeIy through a sleeve 2 in the lower end of the right-hand saw" frame-arm a, sem isth'reade'd at its outer-"end as a't e "and this threaded "endcoopera te's 'withan internally threaded sleeve mcarried 'at the inner end orthe'member 5shaped'at itsouter end at 6 for rotation by a conventional handle. Rota-table upon stud"- member 5 isexternally threaded sleeve Tthreaded through nut 8 whicliis thi'eaded into one end of the enclosing tube 9. This tube-9 carries at the left handend, as shown in -FigJB,

and attached thereto by the screw- Hl'the member I Fthreaded into the end of thetube. This mem benii carries a diski'zl o'pposin disk is carried byth'e' saw frame arm'ov and between these disks are mounted antifriction balls i4. Stud mem berb is provided With "a circular projecting rib iiithe innenface of which contacts disk IS mounted upon thestudl Mounted just inside the disk it'is a second disk i! which carries at its upper end a threaded stud l8 projecting through an opening lfi'in the tube 9. Between disk l'l'and' member H is mount-ed a spiral spring 28; A face of the tube 9 is inscribed at to show in pounds the amount of tension i-Inposed'upon the saw blade by the compression of the spring 25. At the-righthand end of the tube 9 is shown a recess 22 bored out to contain the washer 23 pressed by small spiral spring 24 against the sleeve 1 and' tending to hold this sleeve inany adjusted position as against vibration or accidental displacement."

operation anydesired ten'si'onmay be placed upon the saw'blade B'by turningcf'th-e stud'iil' point such that there is only a small clearance between it and the disk It. This clearance is enough to allow for expansion of the saw, or pin hole stretching, but not enough to cause the ten- 3 sioning device to bounce from the machine should the stud break or a stud strip, the result of which otherwise might be to cause possible injury to parts of the machine and to bystanders.

With the construction as shown when it is desired to change a blade, it is only necessary to unscrew the stud 5 about one turn and all tension is removed. The blade may then be changed and as the spring is held compressed by the sleeve 1 it is only necessary to tighten it again about one revolution and the full load is transferred from the sleeve to tension the blade.

It will be seen that turning of the stud memher 5 rotates the entire tube 9, such rotation being rendered more easy by the ball thrust bearings M which are especially useful when tensioning heavy blades which require tension of two thousand pounds and higher.

It will thus be seen that I have in the construction shown provided a simple, easily assembled, easily operated and efficient device for imposing any desired spring tension upon'the saw blade while at the same time eliminating the liability to damage caused by breakage or stripping of any of the parts, which would permit violent reaction of the tensioning spring in the absence of means for limiting such reaction,

Since certain changes may be made in the above construction and different embodiments of the invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the genericand specific features of the invention herein described, and all statements of the scope of the invention which as a matter of language might be said to fall therebetween.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In a hack. saw blade tensioning device, a hack saw blade, a threaded stud, mounted to permit reciprocation thereof, connected to the lade at one end, an internally threaded sleeve threaded upon the end of said stud, a spiral spring surrounding said sleeve, a follower carried with said sleeve and bearing against one end of said spring whereby rotation of the sleeve in one direction tends to compress said spring and impose a tension upon said saw blade and an adjustable member on the side of said follower away from said blade which can be set to limit the reactive distance of travel of said spring.

2. In a hack saw blade tensioning device, a frame, a blade carried thereby, a reoiprocable stud connected to the blade at one end, said stud being threaded at its free end, an operating stud member carrying an internally threaded sleeve cooperating with the externally threaded end of the saw blade stud, a spiral spring surrounding said sleeve, a tubular member surrounding said spring, a member within said tube connected to said tubular member forming a support for the inner end of said spring and supported against the saw frame, a follower for said spring carried at the other end of said tube, said follower adapted to be advanced to increase the tension of said spring and accordingly the tension upon the saw blade upon rotation of the sleeve in one direction, and a member, threaded into the outer end of said tube, adapted to be set to limit the reactive effect of the return of said spring upon breakage of the saw blade connection.

3. In a hack saw blade tensioning device, a frame, a blade carried thereby, a reciprocable stud connected to the blade at one end, said stud being threaded at its free end, an operating stud member carrying an internally threaded sleeve cooperating with the externally threaded end of the saw blade stud, a spiral spring surrounding said sleevefa tubular member surrounding said spring, a member within said tube connected to said tubular member, forming a support for the inner end of said spring and supported against the saw frame, antifriction bearings interposed between said tube and the saw frame, a follower for said spring carried at the other end of said tube, said follower adapted to be advanced to increase the tension of said spring and accordingly the tension upon the saw blade upon rotatation of the sleeve in one direction, and a member threaded into the outer end of said tube adapted to be set to limit the reactive effect of the return of said spring upon breakage of the saw blade connection.

4. In a hack saw blade tensioning device, a frame, a blade carried thereby, a reciprocable stud connected to the blade at one end, said stud being threaded at its free end, an operating stud member carrying an internally threaded sleeve cooperating with the externally threaded end of the saw blade stud, a spiral spring surrounding said sleeve, a tubular member surrounding said spring, a member within said tube connected to said tubular member forming a support for the inner end of said spring and supported against the saw frame, a follower for said spring carried at the other end of said tube, said follower adapted to be advanced to increase the tension of said spring and accordingly the tension upon the saw blade upon rotation of the sleeve in one direction, a member threaded into the outer end of said tube adapted to be set to limit the reactive effect of the return of said spring upon breakage of the saw blade connection, and a spring-pressed washer bearing against said threaded member tending to hold it as against accidental displacement from its adjusted position.

WILLIAM H. SHORTELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 381,466 Dickerson Apr. 17, 1888 1,205,368 Magin Nov. 21, 1916 2,337,629 Shortell- Dec. 28, 1943 2,411,779 Dillon et a1. Nov. 26, 1946 I FOREIGN PATENTS Number I Country Date 191,105 Great Britain Jan. 1, 1923 356,031 Great Britain Sept13, 1931 797,336 France 'Feb. 8, 1936 

